Known is a method for production of articles from foliated composite material including the placing of impregnated fabric sheet (prepreg) onto the shaping mandrel, the pressurization with the use of vacuum bag, and the shaping of the article under the influence of atmospheric pressure (V. N. Krysin, M. V. Krysin, Technological processes of structures shaping, winding and gluing. Moscow, Mashinostroyeniye, 1989.-240 p., p. 118-125, ISBN 5-217-00533-5).
The main short-comings of herein-presented method are the low output due to high labor expenditures for prepreg sheet placing into the form with complicated relief, the impossibility to produce the folded structure core with dense relief, and expensive relief tooling.
Known is a method for corrugated core shaping with the use of transformable mandrels. This method involves the placing of composite material in the form of prepreg onto the tooling plane surface which is transformed then into the folded structure with the relief geometries required whereupon the folded structure is shaped. For that, with the aim to obtain the high technical characteristics, the given device with the article is put into the autoclave where all the required operating practices realize: the pressure (up to 0.6-0.8 MPa) and the temperature (up to 200° C.) (V. I. Khaliulin, Technological schemes for sandwich structures production, KSTU, Kazan, 1999.-168 p., p. 149-155.—ISBN 5-7579-0295-7).
The main short-coming of herein-presented method is the necessity to expose the shaping tooling to high temperature and pressure resulting in reduction of technological lifespan.
Known is a method for production of articles from foliated composite material including at its first stage the binder discrete application onto the preliminarily marked-out fabric plane sheet along the parts corresponding to folded type core side ridges obtaining thus the zones of unimpregnated fabric along the bond lines of said ridges. At the second stage the unimpregnated fabric in its plane state is put between the heated slabs of the press whereupon under certain temperature and pressure the binder is hardened. At the third stage the development is deduced from the plane state by means of folding-bending along the unimpregnated zones of the fabric. With the aim to impart rigidity to the core, the unimpregnated zones are impregnated with binder whereupon the binder is hardened (RF Patent no. 2,057,647 C1, Int. C1.: B 29 D 9/00. Method for core production from composite material.—Bulletin no. 10 of 10.04.96). The given method is taken as a prototype.
The main short-coming of herein-presented method is the impossibility to execute the first stage when using thin fabrics. The thickness of fabrics used in production of composite articles is 0.1-0.2 mm while the width of unimpregnated fabric parts along the core side edges splice lines should be 0.2-0.4 mm so as to obtain the high accuracy of relief geometries.
Since the material of prepreg reinforcing base (glass fabric, carbon fabric, etc.) has the capillary-porous structure, when applying the binder onto the parts that correspond to folded structure side ridges the binder may penetrate to the zones of bending lines. In this case at the next stage (shaping) when supplying heat to the blank, the active hardening of binder will take place at this zones too; it will disable the blank of mobility along the bending lines and will impede the process of plane blank transformation to 3-D structure.
Since the impregnated fabric is not solid, when placing it onto the press slab for further shaping, required is the accurate correspondence of real ridges dimensions and bending lines with the parameters of the core ideal development and, therefore, with the core parameters in its relief state. This condition is difficult-to-realize and requires the special tooling and additional efforts. The warp of fabric in any direction with the marked-out and impregnated ridges and unimpregnated bending lines results in distortion of folded core structure geometrics.